The basic rationale for the exception is that employees are under a duty to be accurate in observing, reporting, and recording business facts.
The availability of the declarant (the employee whose testimony is being replaced by the record) is immaterial for the purposes of this exception.
The record must have been made at or near the time of the act, event, or transaction at issue.
In the case of Palmer v. Hoffman, 318 U.S. 109 (1943), the Supreme Court of the United States ruled that an accident report created by a railroad company which was prepared in anticipation of a lawsuit by the victim was inadmissible, because it was not prepared in the regular course of business.
Such information is considered admissible separate and apart from privately made business records described above.